This invention relates to an improved extrusion apparatus having an internal deckle system.
An extrusion apparatus having deckles defining the web width, is well known. The deckles may be internal, external, or an external/internal combination such as an external boat deckle with internal deckle members. U.S. Pat. No. 3,829,274 to Melead exemplifies an external/internal combination in which a rack and pinion mechanism provides for adjustment of the external boat deckle and for movement of internal deckle rods. In film extrusion, an external deckle member disadvantageously results in a comparatively larger gap between, and limits the relative positioning of, the exit orifice and chill rolls.
U.S. Pat. No. 3,018,515 to Sneddon teaches a two component, internal deckle with external adjustment provided by a hand-turnable nut. One component is provided by a cylindrical head or manifold plug that precisely fits within the manifold, and a fin that joins into the manifold plug and extends downwardly. The bottom of the fin is formed with a semi-cylindrical groove within which a separately adjustable, closure wire fits.
U.S. Pat. No. 4,248,579 to Maejima teaches a two component, internal deckle with geared, external adjustment. A support rod movably disposed within the manifold, and a flag that extends from an end of the support rod into the preland channel, serve as one component, and a downstream deckle rod is the second component. Adjustment is provided by a rotatable shaft in threaded engagement with an internally threaded bore of the support rod.
A problem with prior art, internal deckle systems is the space requirement of external adjustment mechanisms. This problem is of particular importance when retrofitting existing machinery. Interference with chill rolls must be avoided. Moreover, a simplified, efficient adjustment mechanism would be beneficial.
Additionally, facile and easily repeatable adjustment of the internal deckle components is needed. In typical use of prior art adjustment mechanisms, all deckle components are initially moved as a unit to suitably position the deckle rod and set the slot width. Thereafter, the deckle rod is manually held in place, and final adjustment of the remaining deckle component or components is made. However, holding the deckle rod in place while making adjustment of the remaining deckle component or components may be difficult, and the deckle rod may thereafter need to be reset to the proper position.
A further problem is that fluid pressure acting on the inner ends of the deckle components tends to push them outwardly. A friction brake mechanism for preventing deckle components from being forced out of adjustment, must be unlocked and locked to allow deckle repositioning. Therefore, there is a need for an improved brake mechanism.
U.S. Pat. No. 4,659,302 to Maejima teaches a three component, internal deckle provided by an upper deckle portion that includes a manifold plug; an independently movable, lower deckle portion; and a deckle rod. U.S. patent application Ser. No. 915,485, filed on Jul. 17, 1992, describes a three component, internal deckle provided by an upper deckle plug, an independently movable, deckle blade having a leading edge that may be proximate to the mouth of the preland channel, and a deckle rod.
A drawback with a separately moveable, lower deckle is that under normal operating conditions, inward adjustment may be difficult, and in the case of U.S. Pat. No. 4,659,302 to Maejima may result in support rod deflection. Consequently, to effect inward adjustment, users may reduce or stop flow throughput.
A further drawback is that flow pressure at the inner end of a separately moveable, lower deckle may produce downward deflection and contact with the deckle rod. Contact with the deckle rod may hamper positioning of the rod, and may result in premature failure of the rod.
Thus, there continues to be a need for an improved extrusion apparatus that includes an internal deckle system.